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Re: [YugoUnitedGVOwners] Cam timing

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  • Art Hughes
    I have to double check my 1100 cam. Have a mild cam in it, and was in a hurry when I installed it. I ll have to post the compression figures and cam timing at
    Message 1 of 4 , Apr 22, 2013
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      I have to double check my 1100 cam. Have a mild cam in it, and was in a hurry when I installed it. I'll have to post the compression figures and cam timing at .050 lift, before and after.
      I don't have pistons or head milling to raise above stock compression. Thinking maybe I can advance the cam to add to the bottom end. I can pull 7,000RPM fairly easy in 3rd gear, (75MPH) but more bottom and 6,500 would be fine.
       
      One thing for sure, the idle mix won't adjust in 30 seconds, as the Weber carb is very sensative. 1/16th of a turn on the mix is a big adjustment, when you get close to right. On mine, it takes about 6-8 seconds BEFORE the mix screw turn is fully realized by the engine. Only way I ever had good sucess is using a tachometer to monitor RPM change while adjusting. Plus, after the cooling fan comes on, you have to raise the RPM to 2500 or so, for a minute, to cool down the intake and carb. Won't adjust well when overheated by the exhaust manifold.
      I just did mine a couple weeks ago, and found when I did the cam, I missed it by 1/2 turn, rich, being in too much of a hurry. It does make a big difference in how it runs over all.
       
      Art Hughes  Columbus, Ohio  USA
       
       Visit   www.wvaanne.com   Art's List of Family Connections, WV Rt  87
                           Genealogy in Jackson and Mason Counties, WV
       
                                          



      From: yugophile <joffrey1@...>
      To: yugounitedgvowners2@yahoogroups.com
      Sent: Mon, April 22, 2013 10:49:08 AM
      Subject: [YugoUnitedGVOwners] Cam timing

       

      It was time to change my timing belt and I was all excited to set my cam timing back 10 crank degrees to see if a little miller cycle effect would get me better mpg or allow lower octane gas. I checked it first to see where my cam has been and found that it already was 12 degrees retarded! Compression was 142 psi with the cam like that. Rather than taking it out further, I figured I'd try closer to stock and moved it forward 10. I can feel more bottom end and the idle is more stable. Steady idle has always been elusive on this one, due to the throttle being at the entrance to the supercharger and the large volume of gated air between there and the engine. Compression is 181 on that same cylinder. Higher than I expected. I wonder what other folk measure on standard CR yugos. Didn't have to tweak the ignition timing or fueling for a quick test around the block, but I expect I will to tweak both. It will be interesting to see if I burn more fuel or less.

    • yugophile
      I know that unstable idle is typically due to a lean idle mixture, but that is not the case on mine. I have programable fuel injection with a widband O2
      Message 2 of 4 , Apr 23, 2013
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        I know that unstable idle is typically due to a lean idle mixture, but that is not the case on mine. I have programable fuel injection with a widband O2 sensor. I can get the mixture right. There is just a lot of plumbing between the throttle body and the engine. It's like having a plenum thats too big. When you close the throttle it takes more time for the engine to suck up all that air and create vacuum. Then when it does, the engine slows down so much that more air can slip past the partialy closed throttle than the engine uses so the pressure and rpm start going up. Then it repeats. I could be wrong on whats going on there, but When I disconnect the supercharger and put the throttle bodie back in the stock it idles nice so I know it's not the mixture or the timing. Nothing to do with boost either, as the supercharger bypass is open when there is manifold vac. thanks fo rth eoffer of checking compression. If you have a preformance cam, then that will change your result. I was just wondering what standard stock setups see. I used to think they were like 145 psi for a 1100 and 120 for a stock lower compression 1500.
        Jeff f
        --- In yugounitedgvowners2@yahoogroups.com, Art Hughes <pro4art@...> wrote:
        >
        > I have to double check my 1100 cam. Have a mild cam in it, and was in a hurry
        > when I installed it. I'll have to post the compression figures and cam timing at
        > .050 lift, before and after.
        >
        > I don't have pistons or head milling to raise above stock compression. Thinking
        > maybe I can advance the cam to add to the bottom end. I can pull 7,000RPM fairly
        > easy in 3rd gear, (75MPH) but more bottom and 6,500 would be fine.
        >
        >
        > One thing for sure, the idle mix won't adjust in 30 seconds, as the Weber carb
        > is very sensative. 1/16th of a turn on the mix is a big adjustment, when you get
        > close to right. On mine, it takes about 6-8 seconds BEFORE the mix screw turn is
        > fully realized by the engine. Only way I ever had good sucess is using a
        > tachometer to monitor RPM change while adjusting. Plus, after the cooling fan
        > comes on, you have to raise the RPM to 2500 or so, for a minute, to cool down
        > the intake and carb. Won't adjust well when overheated by the exhaust manifold.
        >
        > I just did mine a couple weeks ago, and found when I did the cam, I missed it by
        > 1/2 turn, rich, being in too much of a hurry. It does make a big difference in
        > how it runs over all.
        >  
        > Art Hughes  Columbus, Ohio  USA
        >  
        >  Visit   www.wvaanne.com   Art's List of Family Connections, WV Rt  87
        >                      Genealogy in Jackson and Mason Counties, WV
        >  
        >                                     
        >
        >
        >
        >
        > ________________________________
        > From: yugophile <joffrey1@...>
        > To: yugounitedgvowners2@yahoogroups.com
        > Sent: Mon, April 22, 2013 10:49:08 AM
        > Subject: [YugoUnitedGVOwners] Cam timing
        >
        >  
        > It was time to change my timing belt and I was all excited to set my cam timing
        > back 10 crank degrees to see if a little miller cycle effect would get me better
        > mpg or allow lower octane gas. I checked it first to see where my cam has been
        > and found that it already was 12 degrees retarded! Compression was 142 psi with
        > the cam like that. Rather than taking it out further, I figured I'd try closer
        > to stock and moved it forward 10. I can feel more bottom end and the idle is
        > more stable. Steady idle has always been elusive on this one, due to the
        > throttle being at the entrance to the supercharger and the large volume of gated
        > air between there and the engine. Compression is 181 on that same cylinder.
        > Higher than I expected. I wonder what other folk measure on standard CR yugos.
        > Didn't have to tweak the ignition timing or fueling for a quick test around the
        > block, but I expect I will to tweak both. It will be interesting to see if I
        > burn more fuel or less.
        >
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